A process of discovering a Wireless Local Area Network (WLAN) Access Point (AP) should be preprocessed to allow a terminal to use a WLAN service. A method of discovering a WLAN AP may be divided into two methods including a passive scanning method and an active scanning method. In the passive scanning method, a terminal receives a beacon frame periodically transmitted (100 ms) by a WLAN AP to identify the existence of the WLAN AP. The passive scanning method may require a maximum time of 100 ms per channel according to a time point when the beacon is obtained. In the active scanning method, when the terminal directly transmits a probe request and the WLAN AP receives the probe request, the WLAN AP transmits a probe response to inform of the existence of itself. The active scanning method takes less time to discover the WLAN AP in every channel as compared to the passive scanning method, but has a burden in that the UE should transmit the probe request. Further, there is another burden in that the WLAN AP should generate a packet in addition to the beacon frame. Accordingly, the prior art (US 20060040656) discloses a method in which a cellular Base Station (BS) is synchronized with a WLAN terminal and the cellular BS informs the terminal of a transmission time of the synchronized WLAN AP, so that the terminal turns on its own WLAN interface according to a beacon receiving time.
Such a prior art requires an interface or a hardware device to synchronize the cellular BS and the WLAN AP. Accordingly, it is difficult to synchronize a WLAN AP which a user has personally installed. Further, there are many WLAN APs within a service coverage of the cellular BS, and thus it is difficult to synchronize the many WLAN APs and the terminal is burdened by many pieces of information provided to the terminal.
Accordingly, an improved WLAN discovering method is currently required.